1. Field of the Invention
This invention relates to implantable medical devices and, more particularly, to a dynamic motion transducer system for use in a chronically implanted medical device. More specifically, the invention discloses a transducer and circuitry suitable for dectecting pressure and other force parameters for use with a pacemaker or other implanted cardiac monitoring and/or treatment device.
2. Description of the Prior Art
Pressure transducers for measuring fluid pressure within the human body are well known in the art from U.S. Pat. No. 4,023,526 to Hynecek, et al. Devices such as that disclosed by Hynecek are typically used in an invasive fashion for temporary diagnostic purposes. Such devices are typically interfaced to signal processing circuitry located in diagnostic equipment located outside of the patient's body.
Recent increases in the complexity of pacemakers and other implantable medical devices have increased efforts at producing sensors and transducers to monitor a variety of physiologic functions. These transducers will allow the exploitation of the additional capability of such medical devices.
A successful sensor or transducer system must have a life expectancy as long as the implanted device which may be as long as ten years in the case of a lithium battery powered pacemaker. Such sensors must be hermetically sealed and must operate at very low current. Additionally, these features must be attained in a device small enough to be passed down a human vein or artery. For these reasons, the aforementioned prior art transducers are not suited for chronic implant applications.